Device for detecting welding of relay

ABSTRACT

In the present invention, the connection between an external power supply and a unit for detecting welding of a relay is disestablished at least when a short circuit is detected, thereby preventing the short circuit from being falsely detected in the event that the short circuit and the welding of the relay can both be detected. A device for detecting welding of a relay detects welding of a relay provided to a path via which a cell is charged by an external power supply. Welding of a power-supply-side relay or a ground-side relay is detected on the basis of a current flowing disproportionately more toward the external power supply than the power-supply-side relay or ground-side relay when a control unit has deactivated the power-supply-side relay or ground-side relay during an interrupting in charging. A disconnecting switch establishes or disestablishes the connection between the external power supply and a weld-detection switch.

TECHNICAL FIELD

The present invention relates to a relay welding detection apparatusthat detects welding of a relay provided to a charging path extendingfrom an external power supply to a storage battery.

BACKGROUND ART

In a charging circuit of an electric vehicle, a relay circuit forconnecting and disconnecting a quick charger to and from a junctioncircuit for connecting a storage battery during charging has been usedheretofore. Such a relay circuit includes mechanical relay contacts(hereinafter, referred to as “relay”) used therein, and such a relay issometimes welded due to an on-off operation during application of a highvoltage and high current. Relay welding detection circuits for detectingthis kind of welding of a relay are known (e.g., see Patent Literature(hereinafter, referred to as “PTL”) 1).

In PTL 1, a dead front relay (DFR) is provided between a charging inletand a neutral point of a motor, and in addition, a voltage sensor isprovided between the charging inlet and DFR. In PTL 1, one DFR is turnedon while the other DFR is turned off, and when the voltage sensordetects a voltage, it is determined that the DFR that has been turnedoff is welded.

Moreover, detection of electrical leakage on a vehicle side using acharger has been known, heretofore (PTL 2).

CITATION LIST Patent Literature PTL 1 Japanese Patent ApplicationLaid-Open No. 2009-100568 PTL 2 Japanese Patent Application Laid-OpenNo. 2010-239845 SUMMARY OF INVENTION Technical Problem

PTL 1, however has a problem in that although the welding of a relay isdetectable, electrical leakage is not detectable. PTL 2 has a problem inthat although electrical leakage is detectable, the welding of a relayis not detectable. In a case where a charger outside of a vehicle isconfigured to detect, as illustrated in PTL 2, electrical leakage in thewelding detection apparatus of PTL 1, the current flows through thevoltage sensor for detecting the welding of a relay during detection ofelectrical leakage. This case involves a problem in that wrong detectionof electrical leakage may occur even when no electrical leakage occurs.

An object of the present invention is to provide a relay weldingdetection apparatus capable of preventing wrong detection of electricalleakage by interrupting the connection between a detection section forwelding of a relay, and an external power supply at least duringdetection of electrical leakage in a case where the welding of a relayand electrical leakage are both detectable.

Solution to Problem

A relay welding detection apparatus according to the present inventionis an apparatus that detects welding of a relay provided to a chargingpath extending from an external power supply to a storage battery, theapparatus including: a detection section that detects welding of therelay based on a current flowing through a region of the charging paththat extends from the relay toward the external power supply, when therelay is turned off during stop of charging; and a switch that opens andcloses connection between the external power supply and the detectionsection.

Advantageous Effects of Invention

According to the present invention, it is possible to prevent wrongdetection of electrical leakage by interrupting the connection between adetection section for welding of a relay, and an external power supplyat least during detection of electrical leakage in a case where thewelding of a relay and electrical leakage are both detectable.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a chargingsystem in Embodiment 1 of the present invention;

FIG. 2 is a flowchart illustrating an operation during detection ofelectrical leakage by a relay welding detection apparatus according toEmbodiment 1 of the present invention;

FIG. 3 is a flowchart illustrating an operation during detection ofwelding of relays by the relay welding detection apparatus according toEmbodiment 1 of the present invention;

FIG. 4 is a flowchart illustrating an operation during detection ofelectrical leakage by a relay welding detection apparatus according toEmbodiment 2 of the present invention; and

FIG. 5 is a flowchart illustrating an operation during detection ofwelding of relays by the relay welding detection apparatus according toEmbodiment 2 of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a detailed description will be given of embodiments of thepresent invention with reference to the accompanying drawings.

Embodiment 1 Configuration of Charging System

A description will be given of a configuration of charging system 10according to Embodiment 1 of the present invention with reference toFIG. 1.

Charging system 10 mainly includes vehicle 150, external power supplyapparatus 160, cable 170, and charging plug 180.

Vehicle 150 runs on storage battery 152 as a power source. Vehicle 150is an automobile that runs on the power of storage battery 152 such as ahybrid electric vehicle (HEV), plug-in electric vehicle (PEV), orelectric vehicle (EV).

External power supply apparatus 160 supplies power to storage battery152 via cable 170 and charging plug 180, thereby charging storagebattery 152. External power supply apparatus 160 is a quick charger orthe like provided to a commercial power supply or a downtown plug-instation. External power supply apparatus 160 detects electrical leakageon vehicle 150. External power supply apparatus 160 does not performcharging on vehicle 150 when detecting electrical leakage.

Cable 170 connects between external power supply apparatus 160 andcharging plug 180.

Charging plug 180 is connectable to power supply connection section 151.Charging plug 180 supplies storage battery 152, via relay weldingdetection apparatus 100, with power supplied from external power supplyapparatus 160 via cable 170.

<Configuration of Vehicle>

A description will be given of a configuration of vehicle 150 accordingto Embodiment 1 of the present invention with reference to FIG. 1.

Vehicle 150 includes relay welding detection apparatus 100, power supplyconnection section 151, and storage battery 152.

Relay welding detection apparatus 100 detects welding ofpower-supply-side relay 101 and welding of ground-side relay 102. Thedetection result of welding of relays detected by relay weldingdetection apparatus 100 is displayed on a display section (notillustrated) provided to vehicle 150, for example. Note that, theconfiguration of relay welding detection apparatus 100 will be describedin detail, hereinafter.

Power supply connection section 151 is connected to relay weldingdetection apparatus 100. Power supply connection section 151 isconnected to charging plug 180, thereby connecting between charging plug180 and relay welding detection apparatus 100. Power supply connectionsection 151 is provided so as to be exposed from the body surface ofvehicle 150, for example. Power supply connection section 151 includespower-supply-side terminal 151 a and ground-side terminal 151 b. Apositive (+) terminal of storage battery 152 is connected topower-supply-side terminal 151 a via power-supply-side relay 101. Anegative (−) terminal of storage battery 152 is connected to ground-sideterminal 151 b via ground-side relay 102.

Storage battery 152 stores the power supplied from external power supplyapparatus 160 via cable 170, charging plug 180, power supply connectionsection 151, and relay welding detection apparatus 100. Storage battery152 is mounted on vehicle 150.

<Configuration of Relay Welding Detection Apparatus>

In Embodiment 1, the connection between welding detection switch 103 andexternal power supply apparatus 160 is disconnected by turning offconnection interrupting switch 104 during a period other than a periodof detecting welding of relays. In Embodiment 1, no current thus flowsthrough electrical leakage detection section 163 via welding detectionswitch 103 when power-supply-side relay 101 and ground-side relay 102are turned off.

A description will be given of a configuration of relay weldingdetection apparatus 100 according to Embodiment 1 of the presentinvention with reference to FIG. 1.

Relay welding detection apparatus 100 mainly includes power-supply-siderelay 101, ground-side relay 102, welding detection switch 103,connection interrupting switch 104, resistor 105, and control section106. Welding detection switch 103 and control section 106 constitute thedetection section configured to detect welding of relays.

Power-supply-side relay 101 is provided to the charging path extendingfrom external power supply apparatus 160 to storage battery 152. Morespecifically, power-supply-side relay 101 is placed in series in thepower line connecting external power supply apparatus 160 and storagebattery 152. The term “charging path” herein refers to a path extendingfrom external power supply apparatus 160 to storage battery 152 whenstorage battery 152 is charged using external power supply apparatus160.

Power-supply-side relay 101 is turned on (ON) by the control of controlsection 106 to connect between external power supply apparatus 160 andstorage battery 152. In addition, power-supply-side relay 101 is turnedoff (OFF) by the control of control section 106 to disconnect externalpower supply apparatus 160 and storage battery 152 from each other.

Ground-side relay 102 is provided to the charging path extending fromexternal power supply apparatus 160 to storage battery 152. Morespecifically, ground-side relay 102 is placed in series in the powerline connecting external power supply apparatus 160 and storage battery152.

Ground-side relay 102 is turned on by the control of control section 106to connect between external power supply apparatus 160 and storagebattery 152. In addition, ground-side relay 102 is turned off by thecontrol of control section 106 to disconnect external power supplyapparatus 160 and storage battery 152 from each other.

Welding detection switch 103 is connected in parallel with the chargingpath. Welding detection switch 103 is a photocoupler havinglight-emitting diode 103A and phototransistor 103B (secondphotocoupler). A collector terminal of phototransistor 103B is connectedto voltage detection terminal Vde of control section 106. An emitterterminal of phototransistor 103B is connected to the body ground ofvehicle 150. An anode terminal of light-emitting diode 103A is connectedto the external power supply side of power-supply-side relay 101. Acathode terminal of light-emitting diode 103A is connected to connectioninterrupting switch 104.

Light-emitting diode 103A lights up when a current of at least apredetermined value flows between power-supply-side relay 101 andpower-supply-side terminal 151 a or between ground-side relay 102 andground-side terminal 151 b.

Phototransistor 103B conducts (is turned on) upon receiving the lightemitted when light-emitting diode 103A lights up. Welding detectionswitch 103 connects between voltage detection terminal Vde of controlsection 106 and the body ground of vehicle 150 when turned on.

In addition, phototransistor 103B does not conduct (is turned off)unless light-emitting diode 103A lights up. Welding detection switch 103disconnects the connection between voltage detection terminal Vde ofcontrol section 106 and the body ground of vehicle 150 when turned off.

Thus, a different voltage value is detected from voltage detectionterminal Vde of control section 106 of control section 106 between thecases where welding detection switch 103 is turned on and turned off.

Connection interrupting switch 104 is connected in parallel with thecharging path and placed in series between welding detection switch 103and power supply connection section 151. Connection interrupting switch104 opens and closes the connection between external power supplyapparatus 160 (or power supply connection section 151 when charging plug180 is not connected to power supply connection section 151) and weldingdetection switch 103. Connection interrupting switch 104 is aphotocoupler having light-emitting diode 104A and phototransistor 104B(first photocoupler). An anode terminal of light-emitting diode 104A isconnected to control terminal Vc2 of control section 106. A cathodeterminal of light-emitting diode 104A is connected to the body ground ofvehicle 150. A collector terminal of phototransistor 104B is connectedto a cathode terminal of light-emitting diode 103A. An emitter terminalof the phototransistor 104B is connected to the external power supplyside of ground-side relay 102.

Light-emitting diode 104A lights up when receiving a predetermined levelcontrol signal from control terminal Vc2 of control section 106.

Phototransistor 104B conducts (is turned on) upon receiving the lightemitted when light-emitting diode 104A lights up. Connectioninterrupting switch 104 connects between welding detection switch 103and external power supply apparatus 160 when turned on.

In addition, phototransistor 104B does not conduct (is turned off)unless light-emitting diode 104A lights up. In other words, connectioninterrupting switch 104 disconnects the connection between weldingdetection switch 103 and external power supply apparatus 160 when turnedoff.

Resistor 105 is placed in series between the external power supply sideof power-supply-side relay 101 and light-emitting diode 103A.

Control section 106 outputs control signal Vryp to make ON/OFF controlof power-supply-side relay 101 to power-supply-side relay 101. Controlsection 106 outputs control signal Vryn to make ON/OFF control ofground-side relay 102 to ground-side relay 102. Control section 106turns off power-supply-side relay 101 or ground-side relay 102 anddetects welding of power-supply-side relay 101 or welding of ground-siderelay 102 while charging stops. During this detection, control section106 detects welding of power-supply-side relay 101 or welding ofground-side relay 102 based on a current flowing through a region of thecharging path that extends from power-supply-side relay 101 to externalpower supply apparatus 160 or a current flowing through a region of thecharging path that extends from ground-side relay 102 to external powersupply apparatus 160.

More specifically, control section 106 detects welding ofpower-supply-side relay 101 or welding of ground-side relay 102 based ona voltage detected from voltage detection terminal Vde to which thecollector terminal of phototransistor 103B is connected. During thisdetection, control section 106 determines that welding ofpower-supply-side relay 101 or ground-side relay 102 has occurred, whenthe voltage detected from voltage detection terminal Vde drops by atleast a predetermined value because a current of at least thepredetermined value flows through phototransistor 103B and turns onwelding detection switch 103. In other words, control section 106detects welding of power-supply-side relay 101 or welding of ground-siderelay 102 based on a detection result of a voltage that varies betweenthe cases where welding detection switch 103 is turned on and off.

For example, control section 106 determines that welding ofpower-supply-side relay 101 or ground-side relay 102 has occurred, whenthe voltage detected from voltage detection terminal Vde changes from an“H” level to “L” level. Note that, a description of the relay weldingdetection method will be given, hereinafter.

The region of the charging path that extends from power-supply-siderelay 101 to external power supply apparatus 160 is path “k1” betweenpower-supply-side relay 101 and power-supply-side terminal 151 a. Inaddition, the region of the charging path that extends from ground-siderelay 102 to external power supply apparatus 160 is path “k2” betweenground-side relay 102 and ground-side terminal 151 b.

Control section 106 outputs a control signal from control terminal Vc2to light-emitting diode 104A to turn on connection interrupting switch104. In addition, control section 106 outputs a control signal fromcontrol terminal Vc2 to light-emitting diode 104A to turn off connectioninterrupting switch 104. Control section 106, for example, outputs an“H” level control signal to light-emitting diode 104A to causelight-emitting diode 104A to light up, thereby turning on connectioninterrupting switch 104. In addition, control section 106 outputs an “L”level control signal to light-emitting diode 104A not to causelight-emitting diode 104A to light up, thereby turning off connectioninterrupting switch 104.

Control section 106 turns off connection interrupting switch 104 duringa period other than a period of detecting welding of power-supply-siderelay 101 and welding of ground-side relay 102.

Control section 106 is electrically insulated from the high voltage side(the direction of external power supply apparatus 160) by weldingdetection switch 103 and connection interrupting switch 104. Note that,a method of detecting electrical leakage will be described, hereinafter.

<Configuration of External Power Supply Apparatus>

A description will be given of a configuration of external power supplyapparatus 160 according to Embodiment 1 of the present invention withreference to FIG. 1.

External power supply apparatus 160 mainly includes power generatingsection 161, input and output section 162, and electrical leakagedetection section 163.

Power generating section 161 supplies power to input and output section162.

Input and output section 162 is connected to cable 170 and supplies thepower supplied from power generating section 161 to cable 170.

Electrical leakage detection section 163 detects electrical leakage onvehicle 150 side. When power-supply-side relay 101 and ground-side relay102 are turned off and power is supplied from power generating section161, electrical leakage detection section 163 detects electrical leakageby detecting a predetermined level voltage. In other words, electricalleakage detection section 163 detects the flow of a voltage which is notsupposed to flow because power-supply-side relay 101 and ground-siderelay 102 are turned off. Electrical leakage detection section 163detects the flow of the voltage which is not supposed to flow as achange in voltage. Note that, the power supplied from power generatingsection 161 during detection of electrical leakage is smaller than thepower supplied from power generating section 161 during charging.

<Operation During Detection of Electrical Leakage of Relay WeldingDetection Apparatus>

A description will be given of an operation during detection ofelectrical leakage of relay welding detection apparatus 100 according toEmbodiment 1 of the present invention with reference to FIG. 2.

In Embodiment 1, control section 106 turns off connection interruptingswitch 104 even before detection of electrical leakage is performed(before operation of step ST201). Accordingly, control section 106 doesnot control opening and closing of connection interrupting switch 104when detection of electrical leakage is performed.

First, control section 106 outputs control signal Vryp topower-supply-side relay 101 to turn off power-supply-side relay 101(step ST201).

Next, control section 106 outputs control signal Vryn to ground-siderelay 102 to turn off ground-side relay 102 (step ST202). Note that theorder of the operations of steps ST201 and ST202 can be reversed.

Next, power generating section 161 starts supplying power for detectingelectrical leakage, and electrical leakage detection section 163 startsdetection of electrical leakage (step ST203).

Next, electrical leakage detection section 163 determines whether or notit has detected a voltage (step ST204).

When electrical leakage detection section 163 determines that it hasdetected no voltage (step ST204: NO), electrical leakage detectionsection 163 determines that no electrical leakage occurs (step ST205).

Power generating section 161 stops supplying power for detectingelectrical leakage, and electrical leakage detection section 163 endsdetection of electrical leakage (step ST206).

Meanwhile, when detecting that it has detected a voltage (step ST204:YES), electrical leakage detection section 163 determines thatelectrical leakage occurs (step ST207).

Power generating section 161 then stops supplying power for detectingelectrical leakage, and electrical leakage detection section 163 endsdetection of electrical leakage (step ST206). Note that when electricalleakage is detected, the user performs an operation to identify whereelectrical leakage occurs and to fix the electrical leakage, forexample.

Note that, when connection interrupting switch 104 is turned on duringdetection of electrical leakage, the current flows in the followingorder: power generating section 161, input and output section 162, cable170, charging plug 180, power supply connection section 151, resistor105, welding detection switch 103, connection interrupting switch 104,power supply connection section 151, charging plug 180, cable 170, inputand output section 162, and electrical leakage detection section 163. Asa result, electrical leakage detection section 163 detects a voltagegenerated during this flow of the current and wrongly detects thatelectrical leakage occurs even when no electrical leakage occurs.Accordingly, in Embodiment 1, connection interrupting switch 104 isturned off during a period other than a period of detection of weldingof relays, thereby, preventing wrong detection of electrical leakage.

<Operation During Detection of Welding of Relays by Relay WeldingDetection Apparatus>

A description will be given of an operation during detection of weldingof relays by relay welding detection apparatus 100 according toEmbodiment 1 of the present invention with reference to FIG. 3.

Relay welding detection apparatus 100 stops charging when detection ofwelding of relays is performed.

First, control section 106 outputs control signal Vryp topower-supply-side relay 101 to turn off power-supply-side relay 101(step ST301).

Next, control section 106 outputs control signal Vryn to ground-siderelay 102 to turn off ground-side relay 102 (step ST302). Note that, theorder of the operations of steps ST301 and ST302 can be reversed.

Next, control section 106 outputs a control signal from control terminalVc2 connected to light-emitting diode 104A to turn on connectioninterrupting switch 104 (step ST303). Thus, relay welding detectionapparatus 100 can detect welding of relays.

Control section 106 determines whether or not the voltage detected fromvoltage detection terminal Vde connected to welding detection switch 103has dropped by at least a predetermined value (step ST304). Controlsection 106, for example, determines whether or not the voltage detectedfrom voltage detection terminal Vde has changed from the “H” level to“L” level.

When determining that the voltage detected from voltage detectionterminal Vde has dropped by at least the predetermined value (stepST304: YES), control section 106 determines that welding ofpower-supply-side relay 101 and welding of ground-side relay 102 occur(step ST305) and skips processing until step ST314 to be described,hereinafter.

Meanwhile, when determining that the voltage detected from voltagedetection terminal Vde has not dropped by at least the predeterminedvalue (step ST304: NO), control section 106 outputs control signal Vrypto power-supply-side-relay 101 to turn on power-supply-side-relay 101(step ST306).

Next, control section 106 determines whether or not the voltage detectedfrom voltage detection terminal Vde has dropped by at least apredetermined value (step ST307).

When determining that the voltage detected from voltage detectionterminal Vde has dropped by at least the predetermined value (stepST307: YES), control section 106 determines that only welding ofground-side relay 102 occurs (step ST308), and thus skips processinguntil step ST314 to be described, hereinafter.

Meanwhile, when determining that the voltage detected from voltagedetection terminal Vde has not dropped by at least the predeterminedvalue (step ST307: NO), control section 106 outputs control signal Vrypto power-supply-side relay 101 to turn off power-supply-side relay 101(step ST309).

Next, control section 106 outputs control signal Vryn to ground-siderelay 102 to turn on ground-side relay 102 (step ST310).

Next, control section 106 determines whether or not the voltage detectedfrom voltage detection terminal Vde has dropped by at least apredetermined value (step ST311).

When determining that the voltage detected from voltage detectionterminal Vde has dropped by at least the predetermined value (stepST311: YES), control section 106 determines that only welding ofpower-supply-side relay 101 occurs (step ST312), and thus skipsprocessing until step ST314 to be described, hereinafter.

Meanwhile, when determining that the voltage detected from voltagedetection terminal Vde has not dropped by at least the predeterminedvalue (step ST311: NO), control section 106 determines that nothingunusual occurs (step ST313).

Next, control section 106 outputs control signal Vryp topower-supply-side relay 101 to turn off power-supply-side relay 101 andalso outputs control signal Vryn to ground-side relay 102 to turn offground-side relay 102 (step ST314).

Next, control section 106 outputs a control signal from control terminalVc2 to turn off connection interrupting switch 104 (step ST315). Thus,electrical leakage detection section 163 can prevent wrong detectionduring detection of electrical leakage.

<Effects of Embodiment 1>

In Embodiment 1, connection interrupting switch 104 is turned off todisconnect the connection between welding detection switch 103 and anexternal power supply during a period other than a period of detectionof welding of relays. Accordingly, wrong detection of electrical leakagecan be prevented in a case where both electrical leakage and welding ofpower-supply-side relay 101 or ground-side relay 102 are detectable.

Moreover, according to Embodiment 1, it is possible to prevent asituation where charging becomes unavailable due to wrong detection ofelectrical leakage even when charging can be performed safely becausethere is no electrical leakage in a system configured to stop chargingwhen detecting electrical leakage.

In addition, according to Embodiment 1, a photocoupler is adopted as thewelding detection switch, so that the control section on the low voltageside can be electrically insulated from the external power supply on thehigh voltage side. As a result, in Embodiment 1, when a quick chargerconfigured to perform charging with a charging voltage of 400V is usedas external power supply apparatus 160, control section 106 can beoperated at 12V which is the same voltage as the conventional case.

Embodiment 2

The configuration of a charging system in Embodiment 2 of the presentinvention is the same as the configuration illustrated in FIG. 1, sothat the description of the configuration is omitted. Note that, adescription will be given in Embodiment 2 using the reference numeralsof relay welding detection apparatus 100 illustrated in Embodiment 1.

In Embodiment 2, connection interrupting switch 104 is turned off todisconnect the connection between welding detection switch 103 andexternal power supply apparatus 160. Thus, in Embodiment 2, no currentflows into electrical leakage detection section 163 via weldingdetection switch 103 while power-supply-side relay 101 and ground-siderelay 102 are turned off.

<Operation During Detection of Electrical Leakage by Relay WeldingDetection Apparatus>

A description will be given of an operation during detection ofelectrical leakage by relay welding detection apparatus 100 according toEmbodiment 2 of the present invention with reference to FIG. 4.

First, control section 106 outputs a control signal from controlterminal Vc2 connected to light-emitting diode 104A to turn offconnection interrupting switch 104 (step ST401). Thus, electricalleakage detection section 163 can prevent wrong detection when detectionof electrical leakage is performed.

Control section 106 turns off power-supply-side relay 101 (step ST402).

Next, control section 106 turns off ground-side relay 102 (step ST403).Note that, the order of operations of step ST402 and step ST403 can bereversed.

Power generating section 161 starts supplying power for detectingelectrical leakage, and electrical leakage detection section 163 startsdetection of electrical leakage (step ST404).

Next, electrical leakage detection section 163 determines whether or notit has detected a voltage (step ST405).

When determining that it has detected no voltage (step ST405: NO),electrical leakage detection section 163 determines that there is noelectrical leakage (step ST406).

Power generating section 161 stops supplying power for detectingelectrical leakage, and electrical leakage detection section 163 endsdetection of electrical leakage (step ST408).

Meanwhile, when determining that it has detected a voltage (step ST405:YES), electrical leakage detection section 163 determines thatelectrical leakage occurs (step ST407).

Power generating section 161 stops supplying power for detectingelectrical leakage, and electrical leakage detection section 163 endsdetection of electrical leakage (step ST408). Note that, when electricalleakage is detected, the user performs an operation to identify wherethe electrical leakage occurs and to fix the electrical leakage, forexample.

Lastly, control section 106 outputs a control signal from controlterminal Vc2 to turn on connection interrupting switch 104 (step ST409).Thus, relay welding detection apparatus 100 can detect welding ofrelays.

Note that, the reason why wrong detection of electrical leakage occurswhen connection interrupting switch 104 is turned on during detection ofelectrical leakage is the same as that of Embodiment 1, so that thedescription of the reason will be omitted. In Embodiment 2, wrongdetection of electrical leakage is prevented by turning off connectioninterrupting switch 104 when detection of electrical leakage isperformed.

<Operation During Detection of Welding of Relays by Relay WeldingDetection Apparatus>

A description will be given of an operation during detection of weldingof relays by relay welding detection apparatus 100 according toEmbodiment 2 of the present invention with reference to FIG. 5.

In Embodiment 2, control section 106 turns off connection interruptingswitch 104 during detection of electrical leakage or during charging andturns on connection interrupting switch 104 during a period other than aperiod of detection of electrical leakage or a period of charging.Accordingly, control section 106 does not control opening and closing ofconnection interrupting switch 104 when detection of welding of relaysis performed. In addition, relay welding detection apparatus 100 stopscharging when detection of welding of relays is performed. Note that,the reason for turning off connection interrupting switch 104 duringcharging is to prevent a charging loss and not to prevent wrongdetection of electrical leakage.

First, control section 106 turns off power-supply-side relay 101 (stepST501).

Next, control section 106 turns off ground-side relay 102 (step ST502).Note that the order of the operations of steps ST501 and ST502 can bereversed.

Next, control section 106 determines whether or not the voltage detectedfrom voltage detection terminal Vde connected to welding detectionswitch 103 has dropped by at least a predetermined value (step ST503).

When determining that the voltage detected from voltage detectionterminal Vde has dropped by at least the predetermined value (stepST503: YES), control section 106 determines that welding ofpower-supply-side relay 101 and welding of ground-side relay 102 occur(step ST504), and thus skips the processing until step ST513 to bedescribed, hereinafter.

Meanwhile, when determining that the voltage detected from voltagedetection terminal Vde has not dropped by at least the predeterminedvalue (step ST503: NO), control section 106 turns on power-supply-siderelay 101 (step ST505).

Next, control section 106 determines whether or not the voltage detectedfrom voltage detection terminal Vde has dropped by at least apredetermined value (step ST506).

When determining that the voltage that has been detected from voltagedetection terminal Vde has dropped by at least the predetermined value(step ST506: YES), control section 106 determines that only welding ofground-side relay 102 occurs (step ST507), and thus skips the processinguntil step ST513 to be described, hereinafter.

Meanwhile, when determining that the voltage detected from voltagedetection terminal Vde has not dropped by at least the predeterminedvalue (step ST506: NO), control section 106 turns off power-supply-siderelay 101 (step ST508).

Next, control section 106 turns on ground-side relay 102 (step ST509).

Next, control section 106 determines whether or not the voltage detectedfrom voltage detection terminal Vde has dropped by at least apredetermined value (step ST510).

When determining that the voltage detected from voltage detectionterminal Vde has dropped by at least the predetermined value (stepST510: YES), control section 106 determines that only welding ofpower-supply-side-relay 101 (step ST511) occurs, and thus skips theprocessing until step ST513 to be described, hereinafter.

Meanwhile, when determining that the voltage detected from voltagedetection terminal Vde has not dropped by at least the predeterminedvalue (step ST510: NO), control section 106 determines that nothingunusual occurs (step ST512).

Next, control section 106 turns off power-supply-side relay 101 andground-side relay 102 (step ST513).

<Effects of Embodiment 2>

In Embodiment 2, connection interrupting switch 104 is turned off todisconnect the connection between welding detection switch 103 andexternal power supply when detection of electrical leakage is performed.Accordingly, wrong detection of electrical leakage can be prevented in acase where both welding of power-supply-side relay 101 or ground-siderelay 102 and electrical leakage are detectable.

Moreover, according to Embodiment 2, it is possible to prevent asituation where charging becomes unavailable due to wrong detection ofelectrical leakage even when charging can be performed safely becausethere is no electrical leakage in a system configured to stop chargingwhen detecting electrical leakage.

In addition, according to Embodiment 2, a photocoupler is adopted as thewelding detection switch, so that the control section on the low voltageside can be electrically insulated from the external power supply on thehigh voltage side. As a result, in Embodiment 2, when a quick chargerconfigured to perform charging with a charging voltage of 400V is usedas external power supply apparatus 160, control section 106 can beoperated at 12V which is the same voltage as the conventional case.

<Variations Common to all Embodiments>

In Embodiments 1 and 2, although photocouplers are used as a weldingdetection switch and a connection interrupting switch, a switch otherthan a photocoupler may be used.

In Embodiments 1 and 2, a relay welding detection apparatus is mountedon a vehicle, but the relay welding detection apparatus may be mountedon not only a vehicle but also an apparatus including a storage battery.

In Embodiments 1 and 2, connection interrupting switch 104 is turned offby the control of control section 106, but connection interruptingswitch 104 may be manually turned off, and as long as connectioninterrupting switch 104 can be turned off at least when detection ofelectrical leakage is performed, any method may be used to turn offconnection interrupting switch 104.

The disclosure of Japanese Patent Application No. 2012-201415, filed onSep. 13, 2012, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The relay welding detection apparatus according to the present inventionis suitable for detecting welding of a relay provided to a charging pathextending from an external power supply to a storage battery.

REFERENCE SIGNS LIST

-   10 Charging system-   100 Relay welding detection apparatus-   101 Power-supply-side relay-   102 Ground-side relay-   103 Welding detection switch-   103A, 104A Light-emitting diode-   103B, 104B Phototransistor-   104 Connection interrupting switch-   105 Resistor-   106 Control section-   150 Vehicle-   151 Power supply connection section-   151 a Power-supply-side terminal-   151 b Ground-side terminal-   152 Storage battery-   160 External power supply apparatus-   161 Power generating section-   162 Input and output section-   163 Electrical leakage detection section-   170 Cable-   180 Charging plug-   Vc2 Control terminal-   Vde Voltage detection terminal

1. A relay welding detection apparatus that detects welding of a relayprovided to a charging path extending from an external power supply to astorage battery, the apparatus comprising: a detection section thatdetects welding of the relay based on a current flowing through a regionof the charging path that extends from the relay toward the externalpower supply, when the relay is turned off during stop of charging; anda switch that opens and closes connection between the external powersupply and the detection section.
 2. The relay welding detectionapparatus according to claim 1, wherein the switch opens the connectionbetween the external power supply and the detection section at leastwhen detection of electrical leakage is performed.
 3. The relay weldingdetection apparatus according to claim 2, wherein the switch opens theconnection between the external power supply and the detection sectionwhen detection of welding of the relay is not performed.
 4. The relaywelding detection apparatus according to claim 1, wherein the switch isa first photocoupler, and the detection section includes: a secondphotocoupler that is turned on when a voltage of the relay on theexternal power supply side is at least a predetermined value; and acontrol section that controls opening and closing of the firstphotocoupler, that detects welding of the relay based on a detectionresult of a voltage that varies between on and off states of the secondphotocoupler, and that is electrically insulated from the external powersupply by the first and the second photocouplers.
 5. A vehiclecomprising the relay welding detection apparatus according to claim 1.